RF signals propagating through a medium generally experience non-linear phase characteristics, namely, phase varies nonlinearly with frequency. Without special processing, such a propagated signal will be detected as a degraded signal.
The prior art has made wide use of tapped delay lines (both digital and analog) which introduce different delays to different frequency components of an RF signal, the components being added at an output of the delay lines so that phase shifts of a propagated signal may be compensated, enabling the compensated signal to resemble the signal before propagation. As a result, information content of an original input signal may be preserved.
Although such prior art devices have been satisfactorily employed for years, they are severely restricted in the number of frequencies that can be handled by the digital electronics circuitry and the speed with which the equalization is activated.